Hydrocarbon dehydration by distillation



Jan. 30,1945.

G. H. .sI-uPLEY, JR., l-:rAL

HYDROCARBON DEHYDRATION BY DISTILLATION` Filei Aug. 26, 1943 Flush Drum zeA AV I l I I .I I I I I I I I I I I I I 30 I l I I l I I I I I I I I I I I I I I I l I I l I I I AI I I I -I I I l H Dry Sidestream Product ATTORNEY.

Patented Jan. 30, 1945 HYDROCARBON DEHYDRATIO'N BY DISTILLATION George H. Shipley, Jr., and William'B. Franklin,

Baytown, Tex., assign ors to Standard Oil Development Company, a corporation of Dela- Ware Application August 26, 1943, Serial No.A 500,092

y 3 Claims.

The present invention is directed to a method for removing water from hydrocarbon mixtures of higher boiling point than propane by distillation. The method of the present invention is applicable to hydrocarbon mixtures heavier than propane in general but is particularly useful in the treatment ofl toluene containing mixtures obtained from petroleum by hydroforming oper- Y ations.

It is known that water dissolved in hydrocarbons behaves with an abnormally high volatility, similar to a light hydrocarbon such as ethane or propane. In accordance with the present invention, advantage is taken of the abnormally high volatility of the water dissolved in hydrocarbons by ash vaporizing part of the total feed of a hydrocarbon fraction heavier than propane and containing dissolved water, condensing the vapors and settling the condensate to separate a water phase and an oil phase. The oil phase is added to the remainder of the feed and the mixture distilled to yseparate the remainder of the water be described in conjunction with the drawing in' which the sole figure is in the form of a diagrammatic flow sheet. A hydrocarbonA feed boiling at a higher temperature than propane and containing -dissolved water enters the system through line I I. By way of example and not of limitation, a feed, which has been satisfactorily processed in accordance vwith the present invention, had an analysis of 1 water, 83% toluene, 15% parafflns higher boiling than toluene and 1% parans lower boiling than toluene. This fraction was obtained by the treatment of a suitably selected petroleum fractionin a hydroforming operation with the subsequent solvent extraction of the hydroformed material and the sulfuric acid treatment and hydrolyzation of the solvent extract with hot caustic soda solution.

The hydrocarbon fraction in line Il passes through heater I2 and into ash drum I3. As the heated mixture enters vessel I3 itsv pressure is reduced allowing a portion of the dissolved water and some of the lower boiling hydrocarbons to vaporize and pass inthe vaporous condition through line IB and. condenser I5 where they are again liquefied and thence into condensate accumulator I6. Vessel IB is arranged to allow the separation of the oil and water layer into fractions by settling and is preferably provided withl yan inner partition I'I to actas a weir.l v

heavier water fraction is withdrawn from' vessel I6 through line I8 and the lighter oil fraction flows over the edge of weir I1 and accumulates in the end' of the vessel adjacent outlet line I9.

The'unvaporized liquid in flash drum I3 isl removed from the bottom of the ash drum by line 20 and the oil fraction from separating vessel I6 is added thereto by means of line I9 containing pump 2|. The combined material is then discharged into distillation tower 22.

In tower 22 the remainder of the'water in conjunction with low boiling hydrocarbons is removed in vaporous form as overheadthrough line 23, liquefied by condenser 24 and discharged into separating vessel25. Vessel 25 is constructed similarly to vessel I6 with an inner partition or weir 26 which allows the withdrawal of a hydrocarbon fraction through discharge line 2l, and a water fraction through discharge line 28. A portion of the light hydrocarbonsfrom vessel 25 is returned to tower 22 as reflux and the remainder is removedby means of outlet 29. The hydrocarbon removedfrom vessel 25 may contain toluene which is recoverable if desired by injecting this stream into additional recovery facilities. It is understood, that the volume of this stream is small in comparison with the amount of toluene recovered by way of line 30. A vsubstantially water-free hydrocarbon is removed from tower 22 as a side stream by means of outlet 30. Heavy hydrocarbon material is removed from'the bottom ofthe tower by means of outlet 3|.

The following is given as a specific example illustrating operating conditions which have been found satisfactory in the operation of the apparatus sho`wn in the figure. The material fed to the apparatus through line II was obtainedv by hydroforming `a suitable :petroleum fraction with subsequent extraction and hydrolyzation thereof to produce a charging stock having as its composition 83% toluene, 15% parafns higher boiling than toluene, 1% paraiiins lower boiling than toluene and 1% of water dissolved in the hydrocarbon mixture. This feed entered the system through line II at a temperature of 310 F. and was heated to 345 F. The line pressure in II was pounds per square inch gauge and the pressure was reduced to 33 pounds per square inch gauge at the ash drum. The evaporation taking place at the fiash drum reduced the temperature of the liquid therein tc 315 F. 'I'he temperature of the condensed vapor discharged The.

into vessel Il was 105 F. and the pressure within this vessel was atmospheric. Distillation co1- umn 22 was operated at a pressure of 10 pounds per square inch gauge. Of the feed charged into the system through line I I, 0.5% was removed as water through line `I8 from the preliminary dashing step and 0.5% was removed as water through line 28 as a separated overhead iraction. 15% of the charge was removed as bottoms through line 3| and 1% of the charge was removed as light hydrocarbon overhead through line 29. 83% of the charge was removed as a side stream through line 30. The material removed as a side stream was nitration grade toluene with a cloud point of 0-10 F.

While the above example has been given showing the application of the present invention to the production of substantially dry toluene, it will be evidentthat it is generally applicable tothe drying of hydrocarbons having boiling points above propane.

dissolved water in conjunction with hydrocar bons in vaporous form from said flashing zone, condensing said vapors and separating the condensed vapors into a water fraction and a hydrocarbon fraction, removing the unvaporized material from said dashing zone, admixing the hydrocarbon fraction therewith and distilllng the admixture to separate substantially the remainder of said water as overhead and a substantially dry hydrocarbon fraction as a side stream.

2. A method for dehydrating a hydrocarbon fraction containing dissolved water comprising the steps of heating a fraction consisting essentially of 83% toluene, 16% of other hydrocarbons and 1% of dissolved water to a temperature oi' approximately 345 F. at a pressure of approximately 10 atmospheres. reducing the pressure of the heated fraction to approximately 2 atmospheres and removing hydrocarbon vapors therefrom and approximately one-half of the water originally dissolved in said charging stock, condensing said mixture and separating the condensed vapors into a water component and a hydrocarbon component, admixing the hydrocarbon component with the unvaporized portion of the fraction and discharging the admixture into a distillation zone maintained 4at a pressure in the range of 1 to 2 atmospheres, removing an overhead from said distillation step including substantially the remainder of the water originally dissolved in the hydrocarbon fraction and a subl stantially dry hydrocarbon as a. side stream.

3. yA method in accordance with claim 2 in which the hydrocarbon material other than toluene in the charging stock includes constituents lower boiling and higher boiling than the toluene and in which the lower boiling hydrocarbon is removed from the distillation step as overhead and the higher boiling hydrocarbon is removed as bottoms.

GEORGE H. SHIPLEY, Jn. WIILIAM B. FRANKLIN. 

